Passive optical networks are becoming prevalent in part because service providers want to deliver high bandwidth communication capabilities to customers. Passive optical networks are a desirable choice for delivering high-speed communication data because they may not employ active electronic devices, such as amplifiers and repeaters, between a central office and a subscriber termination. The absence of active electronic devices may decrease network complexity and/or cost and may increase network reliability.
FIG. 1 illustrates one embodiment of a network 100 deploying fiber optic lines. In the illustrated embodiment, the network 100 can include a central office 101 that connects a number of end subscribers 105 (also called end users 105 herein) in a network. The central office 101 can additionally connect to a larger network such as the Internet (not shown) and a public switched telephone network (PSTN). The network 100 can also include fiber distribution hubs (FDHs) 103 that distribute signals to the end users 105. The various lines of the network 100 can be aerial or housed within underground conduits.
The portion of the network 100 that is closest to central office 101 is generally referred to as the F1 region, where F1 is the “feeder fiber” from the central office 101. The portion of the network 100 closest to the end users 105 can be referred to as an F2 portion of network 100. The network 100 includes a plurality of break-out locations 102 at which branch cables are separated out from the main cable lines. Branch cables are often connected to drop terminals 104 that include connector interfaces for facilitating coupling of the fibers of the branch cables to a plurality of different subscriber locations 105.
An incoming signal is received from the central office 101, and is then typically split at the FDH 103, using one or more optical splitters (e.g., 1×8 splitters, 1×16 splitters, or 1×32 splitters) to generate different user signals that are directed to the individual end users 105. In typical applications, an optical splitter is provided prepackaged in an optical splitter module housing and provided with a splitter output in pigtails that extend from the module. The optical splitter module provides protective packaging for the optical splitter components in the housing and thus provides for easy handling for otherwise fragile splitter components. This modular approach allows optical splitter modules to be added incrementally to FDHs 103 as required. The number of end users may change, however, for example through the addition of new customers to the network or by customers dropping out of the network, and so occasions arise where the module in the FDH 103 needs to be replaced. Additionally, other circumstances may arise when the technician has to visit the FDH 103 to maintain or replace other units.
When replacing equipment, a technician has to disconnect fiber cables from the unit being worked on, and may need to disconnect the fiber cable even when it is just being maintained. Currently, there is no way for the technician to know whether an optical signal is being carried on an optical fiber he or she is about to remove. The only way a technician can determine whether or not a particular fiber cable is carrying an optical signal is to remove the fiber cable and place its output end by a power meter. This is unsatisfactory. For example, a technician may remove a cable carrying an optical signal under the belief that it is not currently carrying an optical signal, which can result in an interruption of service to downstream customers. Also, when checking for breaks, faults etc., it is cumbersome and time consuming to disconnect each fiber cable in turn and measure for the presence of an optical signal.
There is, therefore, a need for a device that permits a technician to easily and quickly, without having to remove a connector, determine whether an optical signal is propagating along the fiber cable.